fix(vite): support virtual:msw imports in vitest

[kettanaito]

• Fixes Can’t import virtual:msw in Vitest #2799

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⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: d23bd731-a543-4182-aa58-f7115d952b65

📥 Commits

Reviewing files that changed from the base of the PR and between 6d6aef1 and 52ce401.

📒 Files selected for processing (8)

• src/vite/options.d.ts
• src/vite/plugin.test.ts
• src/vite/plugin.ts
• src/vite/runtime.ts
• src/vite/tsconfig.build.json
• test/regressions/2799-vite-virtual-module.test.ts
• tsdown.config.ts
• vitest.config.ts

💤 Files with no reviewable changes (1)

• src/vite/options.d.ts

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📝 Walkthrough

Walkthrough

The Vite runtime replaces its preconfigured network export with an asynchronous network factory. The Vite plugin resolves and loads virtual:msw directly, creating a network with server or browser options. Tests and build configuration are updated for this module flow.

Changes

Vite virtual network creation

Layer / File(s)	Summary
Create and manage networks src/vite/runtime.ts	createNetwork(options) waits for prior disposal, creates a network with the supplied options, and applies the existing serialized operations and HMR lifecycle behavior.
Load the Vite virtual network src/vite/options.d.ts, src/vite/plugin.ts, src/vite/plugin.test.ts, src/vite/tsconfig.build.json, test/regressions/2799-vite-virtual-module.test.ts, tsdown.config.ts, vitest.config.ts	The plugin resolves and loads virtual:msw directly, using msw/node defaults for server environments and browser defaults with a worker URL otherwise. The obsolete options module is removed. Tests and build configuration are updated, including a regression test for a registered request handler.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant VitePlugin
  participant Runtime
  participant MSWNetwork
  VitePlugin->>Runtime: createNetwork(options)
  Runtime->>MSWNetwork: defineNetwork(options)
  MSWNetwork-->>Runtime: created network
  Runtime-->>VitePlugin: return network

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Merge Risk: ⚪ Minimal · up to 52ce4

The network replacement concern is resolved by the existing lifecycle logic. No actionable merge blocker remains after normal checks.

Architecture Summary

Architecture risk: 🟡 Medium · up to 52ce4

The change affects 4 systems.

Changed systems: src, tsdown.config.ts, vitest.config.ts, test

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — src (service) was modified; 5 changed files map to changed impact.
• observed — tsdown.config.ts (service) was modified; 1 changed file maps to changed impact.
• observed — vitest.config.ts (service) was modified; 1 changed file maps to changed impact.
• observed — test (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in src/vite/options.d.ts: The virtual:msw/options module declaration and its exported defaultNetworkOptions type were removed.
• observed — Modified behavior in src/vite/plugin.test.ts: The SSR resolution assertion now checks virtual:msw rather than virtual:msw/options.
• observed — Modified behavior in src/vite/plugin.ts: The virtual:msw/options ID constant was removed.
• observed — Modified behavior in src/vite/plugin.ts: resolveId now resolves virtual:msw to its own virtual ID instead of resolving the runtime file, and no longer resolves virtual:msw/options. The loader now handles virtual:msw directly: server environments create a network with msw/node defaults, while other environments create one with browser defaults and record the environment for worker emission. The former options-module loader, which exported defaults separately, was removed.

Reliability and maintainability

• inferred — Risk-relevant change factors for src: blast_radius_1; blast_radius_2; direct_dependents_1; direct_dependents_2

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 6 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: fixing virtual:msw imports in Vitest.
Description check	✅ Passed	The description references issue #2799, which matches the regression fix included in the changeset.

Full details: Docstring Coverage

Explanation

Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 6 files. (1 skipped: 1 unsupported.)

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_{A rabbit watched the network start,
With browser or server options in its heart.
It waited while old networks retired,
Then tested handlers as requests transpired.
HMR paused and resumed with care,
The rabbit left a carrot there.}

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[kettanaito]

Released: v3.0.2 🎉

This has been released in v3.0.2.

• 📄 Release notes
• 📦 View on npm

Get these changes by running the following command:

npm i msw@latest

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